An allose (D-allose) is a rare sugar monosaccharide known as an isomer of psicose, which is an epimer different from glucose (D-glucose) in the —OH group direction of the 3 carbon. The allose has a function of inhibiting thrombogenesis, autoimmune response of organ transplant patient, and proliferation of cancer cell. In addition, there is an effect of prolonging the death of nerve cell after ischemia of liver and brain, and the research has been conducted as a therapeutic drug for leukemia patients.
Due to the above characteristics, the allose has high utility value as the next generation core material in the medical field, but it is extremely rare in nature, and thus it is needed to develop an efficient production process for industrial application. Conventionally, the allose has been produced mainly by chemical synthesis methods, but there is a problem of production of additional saccharides, and complex purification process due to it and generation of chemical waste in the process.
Therefore, in recent years, a method for producing an allose largely using an enzyme which a microorganism produces has been proposed. Izumori group of Japanese Kagawa University has been reported the production of allose from a psicose using a rhamnose isomerase (L-rhamnose isomerase) from Pseudomonas stutzeri (Journal of Fermentation and Bioengineering, 85(5); 539-541, 1998), but the enzyme has a weakness that large amount of altroses (D-altrose) are produced together as by-products during the allose production.
Thus, the development of an enzyme which can exhibit temperature and pH conditions appropriate for industrialization and exhibit high thermal stability without producing by-products as altrose and produce an allose with high yield has been required.